1. Field
The present disclosure relates generally to aircraft and, in particular, to manufacturing aircraft structures. Still more particularly, the present disclosure relates to a system and method for positioning a tool system relative to a structure.
2. Background
In manufacturing aircraft structures, various operations may be performed to assemble each aircraft structure. These operations may be performed manually by human operators using handheld tools or using automated devices. For example, without limitation, drilling, countersinking, fastening, coupling, sealing, coating, inspecting, or other suitable types of operations may be performed to assemble the aircraft structure.
When performing these operations, precise alignment is needed to avoid rework or discarding of parts. The desire for an increased production rate for aircraft structures has led some manufacturers to use automated drilling and fastening systems in addition to or in place of human operators.
With some existing automated systems, the system must contact the surface of the aircraft structure and press against the surface with a prescribed force. These systems may rely on machine global accuracy and tooling to ensure that the drilling tool is oriented in a desired manner relative to the surface and in contact with the surface. With these systems, however, normality measurements, as well as measurement of clamping forces, may not be as accurate as desired. As a result, holes with poor countersink flushness, as well as fastener misalignment to the surface, may occur.
Other existing solutions may employ an end effector with a pressure-sensing nosepiece. The nosepiece may be the first contact point between the end effector and the airplane skin. With a pressure-sensor integrated into the nosepiece, the nosepiece may provide position feedback as the machine contacts the aircraft structure. This system, however, requires contact with the airplane skin to generate such position information. Consequently, the machine must approach the surface slowly to avoid undesired encounters that could cause undesired inconsistencies to form in the airplane skin, the nosepiece, or both. This slow approach may take more time than desired and reduce the speed at which the aircraft structure is assembled.
These nosepiece systems also give rise to reliability and accuracy concerns. Because the nosepiece also provides clamping force for the automated system, the nosepiece must have a large enough diameter to fit various drills, hole inspection probes, and fastener inserters through the center hole. A large contact surface may reduce countersink depth repeatability due to the differing contours in the surface of the aircraft structure.
Additionally, a nosepiece with a large diameter may contact adjacent fastener heads, skin panel lap joints, and debris on the surface of the skin. As a result, the nosepiece may become misaligned, leading to errors when performing operations. Accordingly, there is a need for a method and apparatus that take into account one or more of the issues discussed above as well as possible other issues.